For construction of large structures, material, such as sand, gravel, and dirt, are transported to a construction site using trucks. The trucks carry the material to the construction site and then dump the material into various machines, such as crushers, hoppers, and mixers. Usually, such trucks dump the material into hoppers and the hoppers then feed the material to the various machines. The hopper can have a predefined capacity for retaining a specified amount of material at one time. The trucks should dump the material into the hopper so that the hopper is not overloaded or under-loaded, ensuring an effective and productive feeding of the material to the machines.
Conventionally, a light indicator system is used for controlling the amount of material fed into the hopper. The light indicator system flashes a red light when the remaining capacity in the hopper is less than the full amount of the truck load, thereby preventing the truck from starting to dump its material. The red light may also indicate that the truck must stop dumping the material because the hopper is overloaded. Similarly, the light indicator system may flash a green light when the capacity in the hopper is below a full truck load. The green light indicates that the truck can dump or resume dumping material in the hopper because the hopper is under-loaded.
However, such conventional systems do not take into account the material that is simultaneously being released from the hopper for processing. Therefore, at one end, the hopper is receiving the material from the truck, and at the other end, the hopper is discharging the material for further processing. Neglecting the amount of material being discharged from the hopper may lead to errors resulting in overloading and under-loading of the hopper. This may also result in a delay in dumping the material into the hopper. Specifically, by the time the green light flashes and the truck is ready to dump the material into the hopper, the amount of material in the hopper may further decrease. As a result, the time required for filling the hopper with the material from the truck may also increase. Therefore, accuracy and effectiveness of the dumping of the material into the hopper are compromised. If enough delay is introduced, the discharge from the hopper to the machines can be compromised.
U.S. Pat. No. 4,909,449 discloses a control system for a primary rock crushing stage of a rock crushing plant. A first stage of the rock crushing plant is controlled by controlling a feed rate supplied to a primary rock crusher. Further, the first stage is controlled by indicating to haul vehicles that are transporting rock to the plant from a quarry about the time when the load being hauled can be dumped in to a hopper supplying the feeder for the primary rock crusher. Non-material contacting level sensors, such as ultrasonic transducers are used to sense the level of rock within the hopper and within the cavity of the rock crusher. Further, the load of the motor driving the primary rock crusher and the motor driving an output conveyor that receives the discharged rock from the primary rock crusher is monitored. The output signals from the level and load sensors are compared with preset values to adjust the feed rate of rock being delivered to the primary crusher in order to optimize the throughput of rock in the first crushing stage of the plant. However, the control system is limited to a rock crushing plant. Further, the control system is complicated and expensive.